Hard ferrous alloy



July 7, 1936. F, KORMANN A17 2,046,913

. HARD FERRQUS ALLOY 'Filed may 1,7[1935 MONOTRON D/nmmn Bnnvsu. HARDNESS IIOO - ATTORNEYS Patented July 7, 1936 UNITED STATES HARD FERROUS ALLOY Frederick A. Kormann, Glendale, and Walter F. Hirsch, Huntington Park, Calif., assignors to Industrial, Research Laboratories, Ltd., San Francisco, Calit'., a corporation of Nevada Application May 1'7, 1935, Serial No. 21,962

8 Claims.

This invention relates to ferrous alloys containing boron, and particularly to such an alloy as disclosed in our prior Patent No. 2,025,060, issued December 24, 1935, and has for its object 5 the production of a boronized ferrous alloy which will be of much greater hardness than the alloy described in our patent, yet which will have a melting point sufiicientlylow to permit it to be readily bonded to ordinary preformed steel and 10 iron bodies by being cast thereon to form anintegrally united layer having characteristics not possessed by the supporting metal body and without adversely afiecting the characteristics of the metal of the supporting body. One of the char- 15 acteristics of our ferrous alloy is its extreme hardness and resistance to wear which provides for its wide range of usefulness both as a metal for overlaying other iron and steel articles as well as for articles entirely composed of our alloy. 20 The invention is the result of our discovery of the efiect of the relation of carbon, boron and nickel in cast iron under conditions insuring the substantial absence of graphitie carbon as well as substantial freedom from some of the other 25 elements, commonly found in cast iron.

It has heretofore been knownthat boron when used in steel imparted hardness, but the prior work along this line was carried out with steels of low carbon content or low boron content, or

$ both, so that it may be said that a knowledge of the correct balance or range of permissible and desirable percentage additions of boron, carbon, iron, and nickel, as well as the control of other elements to yield an alloy of the type here under consideration, did not exist, and it is only by our working out of these relations throughyears of experiments and tests in practical applications that/success has been finally achieved.

Our improved ferrous alloy has the following 40 properties:

It is extremely hard and substantially unmachinable except by grinding. Its hardness is inherent in the alloy as cast and may run to over 1000 as measured by the monotron diamond Brinell scale, and it will retain its hardness upon repeated remelting' and casting.

It has amelting temperature ranging from 1950 to 2050 Fahrenheit which is several hundred degrees F. lower than any other hard ferrous or other alloy of comparable hardness.

It has great resistance to abrasive wear; in fact over ten times that of ordinary cast iron.

Its tensile strength runs from about 24,000'to 55 60,000 pounds per square inch.

It bonds readily when melted again t a heated steel or iron body without requiring a flux if the body be clean.

It has an exceptionally low thermal conductivity, being less than a third that of cast iron. 5

It may be produced very cheaply, thus making it adaptable to industrial uses generally without restriction.

Generally speaking, our alloy consists principally of iron, with minor percentage of carbon, boron, and nickel, and controlled other elements.

In composition our improved alloy consists principally of iron, containing carbon within the cast-iron range-that is, from about 2 to 4% by weight-boron ranging from about 0.2 to 2 /2% and nickel from about 1 /2 to 9%. Any other ingredients may be considered adulterants insofar as our alloy is concerned, though some other metals such as manganese, chromium, tungsten, vanadium, molybdenum, cobalt, etc., may be used in various amounts in the alloy where the most favorable characteristics at lowest cost of production of the alloy are not paramount. Thus, small additions of chromium, tungsten, and molybdenum tend to increase the hardness somewhat. Chromium contributes also its wellknown property of increasing resistance to corrosion, and copper similarly. Molybdenum and some others tend to increase the tensile strength.

On the other hand, some of the usual elements found in cast iron, such as sulphur and phosphorus, should preferably be excluded as far as is practicable, or, if present, should generally not 1 exceed about 0.1% for sulphur and 0.3% for phosphorus. In practical work we keep these 'elements each below 0.05%, as both have a deleterious effect on the hardness and quality of the al- 10y. The same, applies somewhat to silicon, except that this eiment may be present in the alloy in amounts up to about 1 /2% without showing 40 appreciableinjuryto the alloy, though about 2 /2% of silicon is about the maximum amount which could be tolerated and this with the higher percentages of boron, as otherwise graphitic carbon may be precipitated in the alloy and which is to be avoided as the carbon in our alloy should be in the combined form. A highly satisfactory grade of our alloy contains butabout 1% of silicon, and the carbon-boronrange should be such as tonot substantially exceed about l /2% of 0 these combined ingredients, 6% being the extreme limit.

The most useful range of ingredients in producing our hard alloy for most industrial uses is as follows, the percentages being by weight of the alloy.

- Percent Carbon from about 2 /2 to 3 Boron do 0.75 to 1 Nickel do 2 to 6 Silicon not over 1 Sulphur do "0.05 Phosphorus do 0.05

Substantially the remainder of the alloy being iron.

Aluminum should be kept out of the alloy, as a small quantity of it causes an appreciable loss of hardness, andtherefore any use of ferroboron Monotron Percentage by weight diamond llrinell Carbon 3. 5 2. 5 2.0 Boron 2 0. 1. 0 500 Carbon 3. 25 2. 5 Boron 0. s l. o

Carbon i. 25 Boron 1.0

Carbon; 3.0 0 Boron 1. 7

The extraordinary effect of nickel in our alloy is shown in the accompanying chart wherein the curve A showsthe hardening effect of additions of nickel from 1 to to an alloy containing about 3% of carbon and 1% of boron, while curve B shows the opposite effect produced by nickel additions to plain cast iron of a t Carbon content without any boron. Both examples were practically free from sulphur and phosphorus and example A contained about 0.57% silicon as against 0.50% for example B which would work slightly in favor of example B as to hardness. It will be seen from curve A that there is a sudden and extraordinary increase in hardness at an addition of 2 /g% to 3/z% of nickel to the boron containing alloy, whereas there is almost as sudden a falling off in hardness in plain cast iron upon additions of the same quantities of nickel. With higher percentages of boron in curve A the hardness would be greater, the range limit of practical usefulness being as previously mentioned.

Our alloy may be made by variously bringing the elements together under fusion in the proportions desired within the ranges given, a source of the boron being an aluminum-free ferroboron with very low sulphur and phosphorus content. Another way is to start with a good grade of cast iron pig preferably containing carbon about 3% or more, silicon from about 2 to 4%, phosphorus and sulphur substantially none, or respectively below 0.3% and 0.1%, and with or without a small percentage of chromium as commonly found in cast iron. The pig iron is melted in contact with borax and in presence of free carbon, as in a graphite crucible or by adding some free carbon, and maintained in molten condition until 5 the desired reduction of the boron from the borax by reaction with carbon and some of the silicon and its absorption into the iron takes place, and the silicon originally present in the iron is greatly reduced by the process. The nickel may be 10 incorporated in the charge or may be melted together with the carbon-boron-iron alloy first produced. The carbon in our finished alloy should all be in the combined form, substantially no graphitic carbon being present, and its fracl5 ture should show a silvery white luster.

The finished alloy may be cast into any form desired, or in ingots for remelting, but if wanted for the hard lining of tubes and cylinders, it is preferably poured out in slabs on an iron plate so that it may be broken into small pieces, cleaned of any scale and foreign matter, as by sand blasting, pickling, or otherwise, and then broken into desirable sizes for easy introduction into tubes to be lined by the centrifugal process, and which hard-lined tubes form the subject matter of our copending companion case filed under Serial No. 21,963 on May 17, 1935.

From the above description it will be seen that our alloy is clearly distinguished in its characteristics from gray cast iron and ordinary white iron as well as the plain boronized cast iron of our copending case under Serial No. 727,278, and has certain properties which either approximate or exceed those of expensive hard alloys and steels, which by reason of their cost and/or high melting point cannot be used for purposes for which our alloy is ideally adapted, and it pro- .vides a cheap cast iron alloy, as distinguished from steel, which has a sufiiciently low melting point to allow it to be readily melted against and bonded to steel and iron cylinders and tubes for lining the same, as well as for other uses where extreme hardness and resistance to wear, such as heretofore found only in expensive alloy steels and other alloys of high melting point, is required. We are fully aware of the former attempts made to improve steel and in some cases iron with the use of boron, but without commercial suc cess because of the failure to recognize the importance of the relation between the carbon and boron range, or carbon boron nickel range, the required-limitation of sulphur, phosphorus, as well as the limitation of silicon to avoid the precipitation of graphitic carbon, and the fact that the 5 carbon present in the alloy must all be in the combined form if the best qualities of the alloy as herein set out are to be secured.

This application is a continuation in part of our copending earlier application, Serial No. 707,035, filed January 17, 1934, which has been expressly abandoned in favor of the present case.

Having thus described our invention, what we claim herein is:

1. A hard substantially unmachinable ferrous alloy consisting principally of iron and containing by weight combined carbon ranging from about 2 to 4%. boron from about 0.2 to 2 1,, nickel from about 1 to 9%, silicon from a trace to about 2 sulphur not exceeding about 0.1% and phosphorus not exceeding about 0.3%, said alloy characterized by a hardness inherent therein as cast above 700 as measured. by the monotron diamond Brinell scale, and a melting point between 1950 and 2050 Fahrenheit.

2. A hard substantially unmachinable ferrous alloy consisting principally of iron and containing by weight combined carbon ranging from 2 to 4%, boron from about 0.2 to 2 nickel from about 2 to 7%, and silicon from a trace to about 2 said alloycharacterized by a hardness inherent therein as cast above 700 as measured by the monotron diamond Brinell scale, a substantial freedom from graphitic carbon, and exhibiting a silvery white fracture.

3. A hard substantially unmachinable ferrous alloy consisting principally of iron and containing by weight combined carbon ranging from 2 to El /2%,, boron from about 0.75 to l nickel from about 2 to 1%, and silicon from a trace to about 1 /2 said alloy characterized by a hardness inherent therein as cast above 700 as measured by the monotron diamond Brinell scale, a substantial freedom from graphitic carbon, and exhibiting a silvery white fracture.

4. A hard substantially-unmachinable ferrous alloy consisting principally of iron and containing by weight combined carbon ranging from about 2 tow/ boron from about. 0.75 to 1 nickel from about 2 to 6%, silicon from a trace to not over about 2 sulphur not exceeding about 0.1% and phosphorus not exceeding-about 0.3%, said alloy characterized by a hardness inherent therein as cast above 700 as measured by the monotron diamond Brinell scale, and a melting point between 1950 and 2050 Fahrenheit.

5. A hard substantially unmachinable ferrous alloy consisting principally of iron withminor percentages of combined carbon, boron, and nickel, said alloy being substantially free from graphitic carbon, and having a hardness inherent therein as cast exceeding 800 as measured by the monotron diamond Brinell scale, a melting point below 2100 Fahrenheit, and exhibiting a silvery white fracture.

6. A hard substantially unmachinable alloy in which iron is the predominant element, said alloy containing, by weight, carbon ranging from about 2 to 3 nickel from about 1% to 8%, boron from about 0.4 to 2/z%, silicon a trace to about 2 sulphur and phosphorus a trace to about 0.1% each, substantially the balance being iron, 10 said alloy characterized by a monotron diamond Brinell hardness above 700 inherent therein as cast, a silvery white fracture, a substantial free dom from graphitic carbon, and a melting point below 2100" F. l5

7.. A hard substantiallyunmachinable alloy in which iron is the predominant element, said alloy containing, by weight, carbon ranging fromabout 2't0 4%, nickel from about 1 to 8%, boron from about 0.2 to 3%. Silicon a trace to about 2 /2%, substantially the balance being iron, said alloy characterized by a monotron diamond Brinell hardness ranging between 700 and 1400 inherent therein as cast, a silvery white fracture,

and a substantial freedom from graphitic carbon.

8. A hard substantially unmachinable alloy in which iron is the predominating element, and containing. by weight combined carbon ranging from about .2 to 4%, nickel from aboutl /z to 10%, boron from about 0.3 to 2 silicon a trace to' about 2 sulphur and phosphorus a trace to about 0.1% each, said alloy characterized by y a m'onotron diamond Brinell hardness in excess of 700 inherent therein as cast, a silvery white fracture, a substantial freedom from graphitic carbon, and a melting point below 2100 F.

'FREDERICK A. KORMANN.

WALTER F. HIRSCH. 

